The present invention, generally, relates to hierarchical storage, more particularly, to management of a location for storing an object in the hierarchical storage.
Cloud service providers often offer different rate plans depending on performance of their services provided. In cloud storage systems, various types of storage devices can be used as backend of the systems for retaining user data. High speed disk storages can be used to improve access performance Low cost tape storage can be also available to reduce cost of the service if users make little account of performance and latency.
Hierarchical storage systems that integrate different types of storage devices including typically high-speed disk storages and low-cost tape storages have been known. In such system, hierarchical storage management (HSM) functionality may actively move user data among the storage devices while making it transparent to a user. Active data that is frequently accessed is stored in the high-speed disk storage. On the other hand, inactive data that is not accessed for a certain period of time is migrated to the low cost tape storage.
By using the hierarchical storage system for the cloud storage service, the cloud service providers can provide their services economically while keeping a certain level of service performance In such system, physical locations of objects such as files in the hierarchical storage may be controlled by the system. End users could not control object locations in the hierarchical storage.
There is still a need for improved hierarchical storage techniques for handling objects among a plurality of storage layers in a hierarchical storage.